The present invention relates to mowers with one or more rotatable organs, each provided with at least one cutting device and driven in rotation by a transmission shaft which cooperates with gears.
Mowers of the above-mentioned general type are known in the art. In known mowers, each rotatable organ or member is rotatably guided in a housing that is air-tight and/or water-tight, and wherein there are also located gears for driving the rotatable organs; and from which the transmission shaft can be pulled out without disturbing the air- or water-tightness of the housing. For transmitting the movement to the gears, the transmission shaft is generally provided with grooves which extend over its entire length, or this can be realized with the aid of a bar which has a constant, for example, hexagonal cross section. The shaft cooperates with one of the gears arranged in the housings which it crosses, and the bore of these gears has a profile which matches the profile of the transmission shaft.
In such a construction, it frequently happens that portions of the metallic, for example steel transmission shaft located between the gears that cooperate with the shaft oxidize in such a manner that the layer of oxide which forms on the shaft surface considerably increases the nominal dimension of the transverse cross section of these portions of the shaft to such an extent that dismounting of the shaft from the housings becomes difficult and in some cases even impossible.
It also frequently happens that during operation of the mower one or the other rotatable organ may be braked in its rotation by an obstacle in its path. If the braking is too great or if the rotatable organ is completely blocked in its rotation, the transmission shaft may be permanently deformed. In this case also, if this permanent deformation is too large, any dismounting of the shaft for repair work becomes a complicated operation.
This dismounting is even more difficult and even impossible when both of the above described events take place on the same shaft at or near the same time.
Mowers are also known in which the transmission shaft and the gears for driving the rotatable organs rotate in a lubricant. In this case the occurrence of oxidation is prevented. There exists the danger, however, that the transmission shaft may permanently be deformed and therefore will be difficult or impossible to remove.
For reducing these risks, it is known to provide transmission shafts with grooves only in the region where the shaft cooperates with the gears, whereas the portions located between these grooves are cylindrical and their diameter is smaller than the diameter of the grooves. Such a shaft, however, is not satisfactory because of its high cost due to difficulties of manufacture. For manufacturing this shaft, a complicated mechanical production process is necessary. The process starts with a workpiece formed as a bar of a round cross section and it must be worked to reduce the diameter of its cross section at portions where the shaft is out of reach with the gears. This operation requires turning and grinding to eliminate any streaks that may have been created during manufacture and which may be the start of a later rupture. The grooves then are cut in a final operation. This production process is even more complicated, as the shaft generally is relatively long.
This shaft has another considerable disadvantage. For mounting this shaft, a first gear must pass a first grooved portion. Then the threading of the shaft continues, so that the first grooved portion disconnects from the first gear which can now turn, in that between the first and the second grooved portions the cross section of the shaft is circular and has a much smaller diameter. In that case when the first grooved portion comes in contact with the second gear and the second grooved portion comes in contact with the first gear, the gears must be turned for a certain angle until all the grooves are aligned in order to make possible to continue threading of the shaft. This is a delicate operation for a single operator. It becomes even more difficult with the subsequent gears, as now there will be three gears to be turned, and so on. In fact, the operator does not even know whether one or more gears are not in place, or in what direction they should be turned, because they are located in a housing. It is to be understood that this mounting is difficult to carry out industrially. Moreover, this difficulty also takes place during dismouting of the shaft for repair.